1. Field of the Invention
The present invention relates to a semiconductor device.
The “semiconductor device” in this specification and the like means all devices that can operate by utilizing semiconductor characteristics. Accordingly, a transistor, a semiconductor element, a semiconductor circuit, a memory device, an imaging device, an electro-optical device, a power generation device (e.g., a thin film solar cell and an organic thin film solar cell), an electronic device, and the like are included in the category of the semiconductor device.
2. Description of the Related Art
In recent years, a flexible device in which a semiconductor element, a light-emitting element, and the like are provided over a flexible substrate has been developed. Typical examples of the flexible device include, as well as a lighting device and an image display device, a variety of semiconductor circuits including a semiconductor element such as a transistor.
As a method of manufacturing a semiconductor device including a flexible substrate, a technique has been developed in which a semiconductor element such as a thin film transistor is formed over a support substrate (e.g., a glass substrate or a quartz substrate), and then the semiconductor element is transferred to a flexible substrate. This technique needs a step of separating a layer including the semiconductor element from the support substrate.
For example, Patent Document 1 discloses a peeling technique using laser ablation as follows. A separation layer formed of amorphous silicon or the like is formed over a substrate, a layer to be peeled is formed over the separation layer, and the peeled layer is bonded to a transfer body with a bonding layer. The separation layer is ablated by laser irradiation, so that peeling occurs in the separation layer.
Patent Document 2 discloses a peeling technique as follows. A metal layer is formed between a substrate and an oxide layer and peeling is performed at the interface between the oxide layer and the metal layer by utilizing weak bonding at the interface, so that a layer to be peeled and the substrate are separated from each other.